1. Field of the Invention
The present invention relates to a motor controlling device.
2. Description of Related Art
A brushless switched reluctance motor in increasing demand has simple structure and low price. The motor has an encoder to output pulse signals synchronizing with a rotor rotation. A number of the output signals output from the encoder are counted, and a rotor rotation position is detected based on the count value. A rotor of the motor is driven by sequentially switching energized phase based on the detection.
This kind of motor with the encoder only detects a rotation angle amount from a start position of the rotor based on the count value of the encoder. JP-A-2004-15849 discloses a motor, and an energized phase of the motor is sequentially changed with a predetermined time schedule during an initial drive after the motor is activated. While a rotor of the motor is rotated, the energized phase is made correspond to a rotation position of the rotor, and signals output from an encoder in a predetermined angle interval are counted. A relationship among the count value of the encoder, the rotation position of the rotor and the energized phase of the motor is learned when the initial drive is ended. In a subsequent usual drive mode after the initial drive, the energized phase is set based on the count value of the encoder and the learned relationship.
It is necessary to continue power supplying for the motor during the initial drive, so that heat is generated from the motor. The initial drive is usually performed only once, because the motor is not turned off for a while after the activation. However, if a user repeatedly turns on and off the motor by intension for fun, the initial drive is repeatedly performed. In this case, the motor may be damaged, or a life of the motor may become short, because a temperature of the motor is unexpectedly raised.